At present, nearly all elements mounted on the circuit boards inside instruments, servers and power supplies have radiation apparatus installed thereon. Fan is one of the indispensable elements in these radiation apparatus. It can disperse thermal energy received by aluminum radiation fins or discharge thermal energy generated by the elements contained in the computers, servers and power supplies outside the casing so that the elements on the circuit boards may function properly without breaking down.
Thus heat dissipation mechanism has become an important procurement criterion of most 1U and 2U servers. The apparatus that adopt rack type structure employ a design different from general information products. They have a flat and narrow space, and electronic elements are densely located in a confined space. They have to overcome a high system resistance to smoothly discharge thermal energy. Hence airflow volume must be sufficiently large and the static pressure must be adequately strong to force and dispel the high temperature outside the machine casing.
Moreover, due to the servers often operate non-stop 24 hours a day, service life of the fans become very important. Once the fans malfunction, the high thermal energy of CPU, chip sets, power supply and memory could break down or burn out at high temperature. Thus the fans used in the servers not only have to withstand high temperature, they also should have durability warranty. Therefore some vendors have designed cooling fan with three essential criteria, i.e. high airflow, high static pressure and long service life.
While most fans used in the servers or power supply of servers have met the criteria mentioned above, in practical configuration the durability of the fans often is shortened. This mainly is caused by the design of heat dissipation arrangement. The fans usually are set to operate independently until they are broken down and replaced by new ones. Another design is to arrange many fans in the server and control in a fault-tolerant fashion. When one fan is down, another fan is activated immediately to carry on heat dissipation for the server to ensure that elements in the server can function properly. However such arrangement still cannot increase the durability of the fans. Moreover, when the rotation speed of malfunctioned fan drops and before other fan is activated, cooling effect cannot be maintained as desired.